Skip to main content

ASP.NET Core MVC–The TypeFilterAttribute

If you have ever created your own Action Filter in ASP.NET Core, you are probably aware of the existance of the ServiceFilterAttribute. But did you know that there exists also a TypeFilterAttribute? In this post, I'll explain both types and show you the differences between the two.

Action Filters that are implemented as attributes and added directly to controller classes or action methods cannot have constructor dependencies provided by dependency injection (DI).  This is because attributes must have their constructor parameters supplied where they're applied.

Therefore ASP.NET Core provides two out-of-the-box attributes that can make your action filters DI enabled:

The ServiceFilterAttribute

The ServiceFilter attribute allows us to specify the type of our action filter and have it automatically resolve the class from the built-in DI container. This means that we can implement our action filter to accept dependencies directly via the constructor:

You should register the filter with the correct lifetime in the DI container:

On your controller classes or action methods you can now add the ServiceFilter attribute:

The TypeFilterAttribute

OK, we’ve seen the ServiceFilterAttribute, but what is then the TypeFilterAttribute and in what ways are they different?

The TypeFilterAttribute is very similar to the ServiceFilterAttribute (and also implements IFilterFactory), but its type is not resolved directly from the DI container. Instead, it instantiates the type by using Microsoft.Extensions.DependencyInjection.ObjectFactory.

Because of this difference, types that are referenced using the TypeFilterAttribute do not need to be registered with the container first. This means that when using a TypeFilter, it is possible to provide the constructor parameters yourself (through the Arguments parameter).

Here is an example (that inspired me for this post) I encountered during a code review:

In the example above, an inherited class is created from the TypeFilterAttribute. This is not necessary, and you can also use it directly(I had to change the filter implementation a little bit):

Popular posts from this blog

XUnit - Assert.Collection

A colleague asked me to take a look at the following code inside a test project: My first guess would be that this code checks that the specified condition(the contains) is true for every element in the list.  This turns out not to be the case. The Assert.Collection expects a list of element inspectors, one for every item in the list. The first inspector is used to check the first item, the second inspector the second item and so on. The number of inspectors should match the number of elements in the list. An example: The behavior I expected could be achieved using the Assert.All method:

Angular --deploy-url and --base-href

As long you are running your Angular application at a root URL (e.g. ) you don’t need to worry that much about either the ‘--deploy-url’ and ‘--base-href’ parameters. But once you want to serve your Angular application from a server sub folder(e.g. ) these parameters become important. --base-href If you deploy your Angular app to a subfolder, the ‘--base-href’ is important to generate the correct routes. This parameter will update the <base href> tag inside the index.html. For example, if the index.html is on the server at /angularapp/index.html , the base href should be set to <base href="/angularapp/"> . More information: --deploy-url A second parameter that is important is ‘--deploy-url’. This parameter will update the generated url’s for our assets(scripts, css) inside the index.html. To make your assets available at /angularapp/, the deploy url should

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.